Regional variability in time-varying transmission potential of COVID-19 in South Korea

Shim, E.; Chowell, G.

In South Korea, the total number of the 2019 novel coronavirus disease (COVID-19) cases is 13,711 including 293 deaths as of July 18, 2020. To examine the change of the growth rate of the outbreak, we present estimates of the transmissibility of COVID-19 in the four most affected regions in the country: Seoul, Gyeonggi Province, Gyeongbuk Province, and Daegu. The daily confirmed COVID-19 cases in these regions were extracted from publicly available sources. We estimated the time-varying reproduction numbers in these regions by using the renewable equation determined by the serial interval of COVID-19. In Seoul and Gyeonggi Province, the first major peak of COVID-19 occurred in early March, with the estimated reproduction number in February being as high as 4.24 and 8.86, respectively. In Gyeongbuk Province, the reproduction number reached 3.49 in February 8 and declined to a value below 1.00 on March 10, 2020, and similarly in Daegu, it decreased from 4.38 to 1.00 between February 5 and March 5. However, the loosening of the restrictions imposed by the government has triggered a resurgence of new cases in all regions considered, resulting in a reproduction number in May 2020 estimated at 3.04 and 4.78 in Seoul and Gyeonggi Province, repectively. Even though our findings indicate the effectiveness of the control measures against COVID-19 in Korea, they also indicate the potential resurgence and sustained transmission of COVID-19, supporting the continuous implementation of social distancing measures to control the outbreak.